This invention relates to a cam selecting device for sewing machines, in which a single operating member is operated to release cam follower from the pattern cam, to shift the cam follower along the packs of cams, and to select a desired pattern cam, thereby to simplify the selection of pattern cams as well as to provide exactly high stitching efficiency.
There have been proposed various kinds of cam selecting devices for a zigzag sewing machine. One example is that two operating dials or buttons are provided for the operator first to push a follower-releasing button with one hand and then to move the follower and select a desired pattern cam by means of the other dial or button with the other hand, this being the so-called two-hand operating system. Such operations are disadvantageous per se, since the releasing button must be continuously pushed usually heavily and the selecting dial is often forcibly rotated by error when the follower is not released or not fully released, resulting in the breakage of the sewing machine.
Another example is that a releasing dial is rotated to set the follower at the released position, and in the meantime another dial moves the follower. In this operation, the manipulation of the operating members is complicated and the operation to cancel the released condition of the follower is often neglected or forgotten.
A further example is that one dial is pushed or pulled to release the followers and the dial is rotated to select a desired cam while maintaining the follower in the released condition with one hand. In this case, the follower releasing pressure is quite heavy, and the dial is often rotated while the follower is not fully released, resulting in disorder of the sewing machine.
A still further example is that the release of a follower and the selection of a pattern cam are carried in one step by rotation of one dial. The rotation angle of the dial is, however, extremely large, since after the follower is released, it is moved and the released condition of the follower is cancelled. Therefore, relative to the pack of built-in pattern cams, the rotation angle of the dial is quite large and the cam selecting operation is difficult.
As above mentioned, the conventional devices have defects and disadvantages and lack in industrial utility.